Clamping mechanisms for conveyor belts typically either clamp along the side edges of the belt or are cross-belt clamps that clamp the belt across the entire lateral width thereof. With the belt clamped, various types of come-along mechanisms can then be connected to the clamps for pulling the belt to perform various maintenance operations thereon. For instance, a typical use of belt clamps is for changing or repairing a splice in the belt. In this instance, clamps will be used on either side of the splice, with the clamp or clamps on one side of the splice being pulled to draw the belt end toward the other end with the other end also pulled toward the opposite pulled end or simply anchored to the conveyor framework via the clamp or clamps thereon for making the necessary repairs to the splice. Because of the tension placed on endless conveyor belts, the belt clamps often experience very high loads. For instance, the takeup roller may apply 2000 lbs of force to the lower run of the belt that the belt clamps will need to overcome if this tension is not released during the belt pulling operation.
Another consideration is the size of the belt clamps. For example, in package handling applications utilizing light duty conveyor belts, there are side panel walls adjacent to the belt side edges for keeping the packages in position on the belt. These side panel walls are typically spaced on the order of approximately ¾ of an inch from the side edges of the light duty belts that carry the packages thereon. Particularly in this type of light duty application, it is desirable for the belt clamps to have a compact configuration so that the user can more easily apply these to the side edges of the belts to be clamped. Accordingly, there is a need for a belt clamp that is of high strength while also having a compact configuration for being clamped on belt edges for the belt pulling operation.
Belt clamps that have a self-locking function are known. Typically, these self-locking belt clamps have a pair of pivotal grip jaws that are pivotally connected to pivot links with the links pivotally connected to a pull loop. When a pull force is applied to the pull loop, the links pivot the gripping jaws into a tight clamping engagement with the upper and lower surfaces of the belt with this clamping force increasing as the pull force increases. In this manner, these belt clamps automatically lock or self-lock onto the belt when the pull force is applied. However, prior to application of the pull force, these belt clamps are not fixed to the belt, and this may make it difficult for users of these belt clamps to locate the clamps at a desired position on the belt. Further, these types of self-locking belt clamps are more susceptible to slippage along the belt prior to application of a sufficiently high pull force so that the jaws exert a sufficient clamping force to keep the jaws clamped and fixed on the belt. Slippage of the contoured gripping surfaces of the jaws along the belt can damage the belt and also can present safety concerns as the pull force is being applied to the clamps.
A belt clamp provided by Watkins Air Support Products allows a user to clamp and lock the belt clamp to the belt prior to the belt pulling operation. The Watkins' belt clamp has a pair of drive screws that both need to be turned to advance the screws into a generally U-shaped housing to drive a belt clamp member into clamped and locked engagement with the conveyor belt in the housing. This is a time consuming procedure as both screws need to be turned before the clamping member is driven sufficiently downward to be clamped against the belt. Further, although the Watkins' belt clamp is prelocked to the belt prior to a belt pulling operation, it does not have self-locking feature such that it has been found that with pull forces of approximately 650 lbs, the belt clamp may slip on the belt. Also, it can be difficult to insure that the same amount of torque force is applied to each drive screw such that the clamp force applied by the clamp member is substantially uniformly distributed thereacross.
Accordingly, there is a need for a belt clamp that is operable to be quickly clamped to a belt. Further, a belt clamp that has both self-locking and prelock features would be desirable.